تاثير پي چند لايه بر روي پارامترهاي جريان نشت از زير سدهاي انحرافي

The Effect of Multi-layer Foundation on Seepage Flow Parameters under the Diversion Dams

در اﯾﻦ ﺗﺤﻘﯿﻖ ﭘﺎراﻣﺘﺮﻫﺎي ﻧﺸﺖ در ﭘﯽ ﻣﻄﺒﻖ دو ﻻﯾﻪ و ﺳﻪ ﻻﯾﻪ ﯾﮏ ﺳﺪ اﻧﺤﺮاﻓﯽ ﺑﻪ ﺻﻮرت آزﻣﺎﯾﺸﮕﺎﻫﯽ ﺑﺮرﺳﯽ ﺷﺪ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ ﺑﺎ اﻓﺰاﯾﺶ ﻫﺪ ﺑﺎﻻدﺳﺖ ﻣﻘﺪار دﺑﯽ ﺧﺮوﺟﯽ اﻓﺰاﯾﺶ ﻣﯽﯾﺎﺑﺪ. روﻧﺪ اﻓﺰاﯾﺶ ﺑﺮاي داﻧﻪﺑﻨﺪي d50= 0.6 mm و d50 mm 1.2 ﻣﯿﻠﯿﻤﺘﺮ ﻣﺸﺎﺑﻪ و ﻣﺤﺪوه ﺗﻐﯿﯿﺮات زﯾﺎد ﺑﻮده اﻣﺎ ﺑﺮاي داﻧﻪﺑﻨﺪي d50= 0.2 mm ﻣﯿﻠﯿﻤﺘﺮ ﻣﺤﺪوه ﺗﻐﯿﯿﺮات دﺑﯽ ﮐﻢ اﺳﺖ. ﺑﺮاي ﭘﯽﻫﺎي دو ﻻﯾﻪ ﺑﻬﺘﺮﯾﻦ ﻋﻤﻠﮑﺮد در ﮐﻨﺘﺮل ﺟﻮﺷﺶ، آراﯾﺶ d50= 0.2 mm و d50=1.2 mm و ﺑﺎ ﻫﺪ ﺑﺎﻻدﺳﺖ 465 ﻣﯿﻠﯿﻤﺘﺮ ﺑﻮد. ﻫﻤﭽﻨﯿﻦ آراﯾﺶ d50= 0.6 mm و d50= 0.2 mm ﺣﺪاﻗﻞ دﺑﯽ ﻧﺸﺖ را ﺑﺪون ﺣﻀﻮر ﭘﺮده آبﺑﻨﺪ در ﺣﺪود 0/266ﻣﯿﻠﯽﻟﯿﺘﺮ ﺑﺮ ﺛﺎﻧﯿﻪ داﺷﺖ. در ﺣﻀﻮر ﭘﺮده آبﺑﻨﺪ ﻧﯿﺰ ﺑﻬﺘﺮﯾﻦ ﻋﻤﻠﮑﺮد در ﮐﻨﺘﺮل دﺑﯽ ﻧﺸﺖ آراﯾﺶ d50= 0.6 mm, d50=0.2 mm ﺑﻮد و دﺑﯽ ﻧﺸﺖ در ﺣﺪود 0/066 ﻣﯿﻠﯽﻟﯿﺘﺮ ﺑﺮ ﺛﺎﻧﯿﻪ ﺑﻪ دﺳﺖ آﻣﺪ. در ﮐﻨﺘﺮل ﮔﺮادﯾﺎن ﻫﯿﺪروﻟﯿﮑﯽ، در ﺣﺎﻟﺖ ﺑﺪون ﭘﺮده آبﺑﻨﺪ و ﺑﺎ ﭘﺮده آبﺑﻨﺪ ﺑﻬﺘﺮﯾﻦ ﻋﻤﻠﮑﺮد ﺑﻪ ﺗﺮﺗﯿﺐ ﻣﺮﺑﻮط ﺑﻪ آراﯾﺶ d50= 1.2 mm, d50= 0.6 mm و d50= 0.6 mm, d50= 0.2 mm ﺑﻪ ازاي ﻫﺪ ﺑﺎﻻدﺳﺖ 410 ﻣﯿﻠﯿﻤﺘﺮ در ﺣﺪود 0/002 و 0/0011 ﺑﻮد. در آراﯾﺶ ﺳﻪ ﻻﯾﻪ، آراﯾﺶﻫﺎي ,d50= 0.6 mm, d50=1.2 mm d50= 0.2 mm و d50=1.2 mm, d50= 0.6 mm, d50= 0.2 mm ﺑﻬﺘﺮﯾﻦ ﻋﻤﻠﮑﺮد را در ﮐﻨﺘﺮل ﭘﺪﯾﺪه ﺟﻮﺷﺶ داﺷﺘﻨﺪ ﺑﻪﻃﻮريﮐﻪ ﺑﻪ ﺗﺮﺗﯿﺐ ﺑﻪ ازاي ﻫﺪ ﺑﺎﻻدﺳﺖ 490 ﻣﯿﻠﯿﻤﺘﺮ و 480 ﻣﯿﻠﯿﻤﺘﺮ اﺗﻔﺎق اﻓﺘﺎد. ﺑﻬﺘﺮﯾﻦ آراﯾﺶ ﺑﻪ ﻟﺤﺎظ ﮐﻨﺘﺮل دﺑﯽ ﻧﺸﺖ ﺑﺪون ﺣﻀﻮر ﭘﺮده آبﺑﻨﺪ و ﺑﺎ ﭘﺮده آبﺑﻨﺪ آراﯾش d50= 0.2 mm, d50 0.6 و d50= 0.2 mm, d50=1.2 mm, d50= 0.6 mm ﺑﻮد ﮐﻪ ﻣﻘﺪار دﺑﯽ ﻧﺸﺖ ﺑﻪ ﺗﺮﺗﯿﺐ در ﺣﺪود 0/533 و 0/433 ﻣﯿﻠﯽﻟﯿﺘﺮ ﺑﺮ ﺛﺎﻧﯿﻪ ﺑﻪ دﺳﺖ آﻣﺪ. ﺑﺮرﺳﯽ ﻧﺘﺎﯾﺞ ﭘﯽﻫﺎ ﻧﺸﺎن داد ﮐﻪ اﺳﺘﻔﺎده از ﭘﯽﻫﺎي ﭼﻨﺪ ﻻﯾﻪ ﻣﯽﺗﻮاﻧﺪ راﻫﮑﺎري ﻣﻮﺛﺮ در ﮐﺎﻫﺶ ﮔﺮادﯾﺎن ﻫﯿﺪروﻟﯿﮑﯽ، ﮐﻨﺘﺮل ﭘﺪﯾﺪه ﺟﻮﺷﺶ و دﺑﯽ ﻧﺸﺖ ﺑﺎﺷﺪ

In this study seepage factors in two-layered and three-layered foundation of a diversion dam was investigated experimentally. Results showed by increasing the upstream head, outlet discharge increases. The trend of discharge increase was similar and the variations range was high for d50=0.6 mm and d50=1.25 mm, but the range of discharge variations was low for d50=0.24 mm. For two-layered foundations, the arrangement of D50=0.2 mm and D50=1.2 mm with 465mm upstream head was the best performance for piping control. Also the arrangement of D50=0.6 and D50=0.2 mm without cutoff had the least seepage discharge (about 0.266 mlit/s). In the presence of cutoff, the best performance for piping control was obtained for the arrangement of D50=0.6-0.2 mm and the seepage discharge was about 0.066 mlit/s. The arrangements of D50=1.2 mm, D50=0.6 mm without cutoff and D50=0.6 mm, D50=0.2 mm with cutoff had the best performance for hydraulic gradient control which were about 0.002 and 0.0011 for 410 mm upstream head, respectively. For three-layered foundation, the arrangements of D50=0.2 mm, D50=0.6 mm, D50= 1.2 mm and D50=1.2 mm, D50=0.6 mm, D50=0.2 mm showed the best performance for piping control so that piping was happened in 490 and 480mm upstream heads, respectively. The best arrangements in terms of seepage discharge control, without and with cutoff were respectively (D50=0.2 mm, D50=0.6 mm, D50= 1.2 mm) and (D50=0.2 mm, D50=1.2 mm, D50=0.6 mm) with 410mm upstream head, in which the seepage discharges were obtained about 0.533 and 0.433 mlit/s, respectively. The results of this study showed that the multi-layered foundations could be considered as an effective alternative in reduction of outlet gradient and control of piping and seepage discharge.